Treatment of hydrocarbon oils



remedying this deficiency. has so Patented Dec. 11, E934 ATES 1,983,693 TREATMENT 0F HYDROCARBON oiLs Gustav Eglofl, Chicago, 111., assignor to Universal Oil Productsflompany, Chicago, 111., a corporation of Delaware No Drawing. Application March 29, 193e, Serial No. 663,342

4 Claims. (Cl. leec) "1:; invention reiers more particularly to the treatment of the lower boiling fractions of crude petroleums which comprise what are known as natural gasolines and straight run gasolines.

In a more specific sense the invention has ref erence to a process of treatment whereby such lower boiling fractions are selectively converted to produce maximum practical yieldsof hydrocarbons hciling within the range of commercial gasolines, the fractions thus produced having at the same time improved antiknock characteristics.

The term natural gasoline is generally applied to gasolines recovered from casinghead gases either by absorption, compression or refrigeration methods and consists principally of paramn hydrocarbons of from 3 to 6 carbon atoms to wit, propane, butanes, pentanes and hexanes though there may be minor amounts of higher boiling paramns present and also small percentages of dissolved hydrocarbon gases depending upon. the conditions of recovery employed. Similarly products falling within the category of natural gasolines are obtained from vapor recovery systems on crude and in some cases on refined storage. The term as used in the present sense comprises also low boiling hydrocarbon fractions obtained from stabilizer unitsapplied either to straight run gasoline or their corresponding cracked products. The fractions from cracked gasoline stabilizers will contain in addition to paraflin hydrocarbons variable percentages of the corresponding oleflns of the same number of carbon atoms. The term straight run gasoline as employed within the meaning of the present specification includes gasoline range boiling fractions produced as aresult of the primary noncracking distillation of crude petroleums. In the majority of cases such gasolines are all of a predominantly paraflln'ic character and as such possess a realtively low knock rating which limits their sales value.

The utilization of natural gasolines has been limited on account of their high vapor pressure,

which limits the amounts which can be safely blended with higher boiling range fractions without causing vaporlock troubles. Owing to -the .iact that there hasxbeen a greater production of Y these gasolines thancould be absorbed by the gasoline trade practically all of the propane and a large percentage of the butanes is being so? pressure in cylinders domestic or wel ing gas.

Utilization of straight run gasoline's is primarily limited by their generally low antiknock value and the principah method of attack for far been along the line of cracking to increase their antiknock value. In one specific embodiment the present invention' comprises treatment or natural and/or under straight run gasolines in two steps. In the first step they are cracked to produce optimum yields of olefins, and in the second step the olefins are polymerized by contact with phosphoric acidto produce gasoline boiling range hydrocarbons of improved antiknock value.

It is the object of the present invention to produce the most economical yields of gasoline boiling range fractions and at the same time the maximum antiknock value in the products consistent with the yield. To accomplish this dual object necessitates the control of the cracking conditions of the first step to produce maximum yields of olefins for forming polymers boiling within the range of motor fuels, say below 437 F. and possessing high antiknock characteristics, usually about 50% higher than iso-octane which is at present used as a standard of reference. To limit the reactions of decomposition of low boiling 'paraifins to the production of high yields of oleflns rather than compounds of ring structure usually requires relatively high temperatures, moderate to low pressures and short time factors since the olefins are produced by initial decomposition reactions apparently cordrocarbons to form equivalent molecules of paraflins and olefins of one-half the molecular weight. This theory of the central scission of straight chain parafiins is convenient in explaining many or the observed results obtained in cracking paramn hydrocarbons though it may not be entirely adequate tocover all cases or all types of products.

The conditions chosen for initially cracking any particular low boiling paraffinic gasoline will de pend primarily upon its boiling range though in general it canbe stated that for natural gasolines falling under the generally accepted term that temperatures of from 1100 to 1500 F., pressures of from atmospheric to as low as 50 mm. of mercury absolute and time factors of less than one second comprise the usual range of operating conditions which may be varied to suit individual cases.

In the' case of straight run gasolines which may be of higher mean boiling range than natural gasolines, slightly lower temperatures may be employed say within the range of 1000 to 1300 F. and pressures from moderately superatmospheric to some lower limit corresponding to a definite vacuum.

In all cases the low boiling gasolines may be fractionated andindividual fractions treated according to their special requirements while the olefins produced. are either recombined and treated en massev with the'preferred catalyst in the second stage or polymerized separately and blended later;

responding to the splitting of straight chain hyinvention the following table is introduced which shows some of the low boiling olefins along with their formulas and boiling points which may be effectively polymerized to form essentially dimers tions and increase the capacity. of commercial equipment though such admixtures must be made with caution if yieldsvof desired products are to be kept high.

and trimers by contact with phosphoric acid an- In the formation of polymers from olefins, parder controlled conditions: 7 ticularly those from mono olefins produced in the e 7 Table I g Formula Boiling point o.

gi ii ylelm 8E1; C H, 102. 7

on 48' aseous g thyl ethylene (li-blltylene) oniomon on, g -50 ggfigg- }Dimethyl ethylene (lsobutylene) on..on=on.cm 1; Unsym. dimethyi ethylene (iso-butylen'e) CH3)2CCHI 6 n-propyl ethylene (alpha-amylene) H:CH:CH1CH=CH: +39 Isopropyl ethylene (alpha-isoamylene) CEfihCHDH-CH; +21 Sym. methyl ethyl ethylene (beta-amylene) CgaQ 1%f.0H=CH.CH;; +38

Unsym. methyl ethyl ethylene gamma-amylene: C=CH1 +31 Trimethyl ethylene (beta-isoamylene) om),=c=cn.om +36 Tetramethyl ethyl n CH;)1C=C(CH3), +73

I have found that by suitablecontrol of temperature and the strength and quantity of phosphoric acid employed, the'polymerization of the lower boiiing oleflns produced in the primary cracking step may be halted before the formation of high boiling, resinous or gummy polymers has taken place to any appreciable extent. As a general rule it is only necessary to prevent excessive temperature rise under which conditions ordinary concentrated phosphoric'acid may be used corresponding to 85 to 90% by "weight of H2PO4. While it. is preferred to use the better known and .more readily available phosphoric acid it is not outside the scope of the invention to employ any of the known acids of phosphorus alone or in suitable admixtures although the results obtained i by these different alternatives -will obviously not be exactly equivalent. As a matter of reference the following table is given to show the different acids of phosphorus along with their formulas and their melting and decomposing temperatures.

" Acids of phosphome Pyro Ortho The following table shows the boiling points of dimers of mono oleflns from 3 to 6 carbon atoms inclusive, and indicates that they are all within formed by the union of one molecule of propylene with one molecule of butylene.

Boiling points of olefin dimers Hexylene... 155 F 255 F ylene Dimer ol hexylene 417 F when the olefinic mixtures from the first step are of such a character that there is less tendency for too extensive polymerization to occur, that is, when they are principally mono olefins, minor amounts of sulphuric acid may be mixed with the phosphoric catalyst to accelerate the reacfirst step of the processdt is probable that their polymerization is preceded by the formation of phosphoric or phosphorous esters which under the conditions of treatment are relatively unstable and decompose to release'the olefin molecules with an increased energy content so that the polymerization reactions result. The exact mechanism of these reactions, however, is not well known and the explanation is not ofiered occurs so that the consumption of acid is small a and a given amount may be used repeatedly without the necessity for purification steps which must be employed in removing sludge products from sulphuric acid. Neither phosphoric nor phosphorous acid has any pronounced oxidizing 26. 5 Above M. P. 70. 0 P30; 38. 0 P30 55. 0 70 P101. Sublimes. P105. P10 38. 6 Hi0 BC 213 action under the preferred conditions of treatment so that condensation reactions due to removal of hydrogen or abstraction of water are substantially absent. The polymerizing action of such' metal halides as anhydrous aluminum chloride and zinc chloride of varying degrees of hydration is frequently too vigorous to render their use safe in the present connection.

The invention is not limited to any particular type of equipment or any specific mode of procedure which may be employed either in the first or the second steps. In the first or cracking step the usual heating coil and reaction chamber hookups of cracking plants may be I modified to some extent so that the necessary short time factors corresponding to optimum olefin'production are made possible. Thus the heating coils may be considerably shortened and constructed of refractory materials which have substantially no tendency to deformation at high temperature when subjected to external pressure conditions corresponding to vacuum operation.

The maintenance of vacuum during the heating period is usually best effected by removal of fixed gases from the liquid receiver rather than by the pumping of hot vapors, though obviously the cool fixed gases may contain sufliciently large.

'for a time best determined by trial, the mixture being either mechanically agitated or circulated to and from a closed pressure container. The amount of phosphoric acid or solution thereof which it is necessary to use in any case will depend upon the character of the reacting olefins and the degree of polymerization desired but in general relatively large volumes of acid are used frequently in the ratio of equivalent molecular weight in reference to the particular olefin or mixture of olefins being subjected to polymerization. However, substantially none of the acid is consumed in the treatment and asv there is substantially no solubility of reaction products in the acid it may be reused repeatedly without regeneration or purification and, consequently,

the amount of acid actuallylost in producing polymerization reactions is of a neglible value and due principally to unavoidable accidents.

When it is desired to polymerize olefin mixtures containing large percentages of propylene and the butylenes which are gaseous at ordinary temperatures, they ,may' be pumped into a pressure treater containing the phosphoric acid during agitation of the latter or they may be preliminarily compressed to liquid and handled in the same way as the amylenes or other ole-fins which are liquid at the temperature of treatment.

As an example of the application of the process to the more efficient utilization of natural gasolines, the following is given though it is merelyselected from a large number of other examples of a similar character.

A natural gasoline produced by compression and absorption of casinghead gases in the field may have the following approximate composition:

Composition of natural gasoline Percent Fthane Propane Butanes Pentanes- Hexanes Higher paraflins Composition of cracked gases- Percmt Hydrogen .;l h

Pantanes The liquid portions of the cracked products from the first step may be thoroughly agitated with about 20% by volume of 89% phosphoric acid and the gaseous products passed therethrough at a slow rate to insure most effective action. By this procedure there may be produced on a basis of the original gasoline approximately of a mixture of hydrocarbons boiling within the range of gasoline as from to 415 F. having an octane number'of and consisting of the pentanes and hexanes still remaining in the cracked mixture plus the polymers from substantially all of the olefins. Thus whereas only about 40% of the original natural gasoline fraction could be employed as blending material in gasoline mixtures, the product of the present process can be completely blended and the increase in volunie of of natural and straight-run gasoline to produce a,

commercial anti-knock automotive fuel, comprising subjecting said gasoline to thermal cracking conditions of temperature and pressure to form therein polymerizable olefines, and thereafter polymerizing the cracked product by subjecting the same to the action of an acid of phosphorus.-

2. A process for increasing the anti-knock value of natural and straight-run gasoline to produce a commercial anti-knock motor fuel, which comprises subjecting said gasoline to thermal cracking conditions of temperature and pressure within 'a heating zone to effect the formation of polymerizable olefines in the cracked product, and thereafter subjecting the resultant mixture of 'vaporous and liquid olefines to a polymerizing treatment in the presence of an acid of phosphorus.

3. A process for increasing-the anti-knock value of natural and straight-run gasoline to produce a commercial anti-knock motor fuel, which comprises initially subjecting said gasoline to cracking conditions of temperature and pressure within a heating zone to induce the formation of olefines within the cracked product, and thereafter treating the resultant mixture of vaporous and liquid olefines with phosphoric acid to polymerize said olefines.

4. A-process for increasing the anti-knock value of natural and straight-run gasoline to produce a commercial anti-knock motor fuel, which comprises initially subjecting said gasoline to cracking conditions under a temperature ranging from 1000" F. to 1500 F. and at substantially atmospheric pressure to form substantial amounts of gaseous and liquid olefines within the cracked product, and thereafter polymerizing the olefine content thereof by contacting the cracked product with phosphoric acid.

GUSTAV EGLOFF. 

